The field of the invention is programmable controllers, and particularly, means for loading and editing programs for controllers such as that disclosed in U.s. Pat. No. 3,810,118 entitled "Programmable Matrix Controller" and that disclosed in U.S. Pat. No. 3,942,158 issued on Mar. 2, 1976 and entitled "Programmable Logic Controller".
Controllers such as those described in the above cited patents perform complex control jobs in accordance with a stored program. The stored program is a set of instructions which directs the controller to examine the condition of various sensing, or input devices such as switches and photoelectric cells, compare these conditions to the conditions specified in the stored program, and accordingly, direct the controller to energize or deenergize selected output devices such as motors, solenoids and lights. Although suitable programs may be developed and loaded directly into the controller, in practice such initial programs must first be used on the job site to correct unforeseen problems which inevitably occur. To this end, program loaders such as that disclosed in U.S. Pat. No. 3,798,612 entitled "Controller Programmer" and that disclosed in U.S. Pat. No. 3,813,649 entitled "Controller Program Editor" have been developed to facilitate the loading and editing of such programs. Such program loaders are separate instruments which are temporarily connected to the programmable controller to allow the entry and manipulation of the control program instructions. When the programmable controller has been successfully programmed and the controlled machine is operating properly, the program loader is disconnected therefrom and may be used to program another system.
Some of the numerous sensing and operating devices on the machine being controlled may be remotely located, or located in relatively inaccessible places. Often during the initial programming of the system, or later when troubleshooting malfunctions in the system, it is desirable to observe the operation of selected sensing devices or operating devices to ascertain whether or not they are operating properly